The invention relates to a very high speed type variable speed motor drive system for driving an air compressor or the like, and, more particular, to an air generating source using a very high speed permanent magnet type electric rotating machine system.
Permanent magnet type synchronous motors have been frequently used, by virtue of their high electric motor efficiency, for industrial drive sources. In the case of motors having low speeds, permanent magnets are attached to a shaft in use, but in the case of motors having high speeds, there is the possibility that permanent magnets are scattered.
As a measure of solving the above-mentioned disadvantage, Japanese Patent Unexamined Publication No. H10-243586 discloses an arrangement of carbon fibers or a titanium ring on an outer periphery of a permanent magnet in very high speed permanent magnet type synchronous motors.
The above-mentioned prior art involves a problem that while a permanent magnet can be prevented from scattering, no consideration is taken of loss generated in a rotor when a permanent magnet type synchronous motor is driven by an inverter and pulsating magnetic flux caused by harmonic current is made to enter the rotor. Further, the prior art does not take consideration of the function of an air generating source drive system when a very high speed permanent magnet type synchronous motor is used for air generation.
It is an object of the invention is to provide a very high speed permanent magnet type electric rotating machine system, in which loss caused in a rotor is small even when driven by an inverter acting at a fundamental frequency of at least several hundred Hz, and so it is possible to achieve high efficiency of an air generating source, and an air generating source using the above-mentioned very high speed permanent magnet type electric rotating machine.
In a first aspect of the invention, there is provided a very high speed permanent magnet type electric rotating machine system comprising a permanent magnet type synchronous motor including a stator having armature windings wound in a plurality of slots formed in a stator core, and a rotor including a conductive permanent magnet provided on an outer periphery of a shaft made of a conductive magnetic material and a reinforcement material made of carbon fibers and provided on an outer periphery of the permanent magnet, and an inverter for driving the permanent magnet type synchronous motor, the improvement comprising an electromagnetic steel sheet ring provided on the outer periphery of the shaft of the rotor, and an reactor interposed between the inverter and the permanent magnet type synchronous motor, and wherein content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor from the inverter are such that when a content percentage of a fundamental wave is 100%, a content percentage B of a seventh order component is at most 10% and the relationship (A less than C less than B) is satisfied where A is a content rata of a fifth order component and C is a content percentage of an eleventh order component.
In a second aspect of the invention, there is provided a very high speed permanent magnet type electric rotating machine system comprising a permanent magnet type synchronous motor including a stator having armature windings wound in a plurality of slots formed in a stator core, and a rotor including a conductive permanent magnet provided on an outer periphery of a shaft made of a conductive magnetic material and a reinforcement material made of carbon fibers and provided on an outer periphery of the permanent magnet, and an inverter for driving the permanent magnet type synchronous motor, the improvement comprising an electromagnetic steel sheet ring provided on the outer periphery of the shaft of the rotor, and an reactor interposed between the inverter and the permanent magnet type synchronous motor, and wherein content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor from the inverter are such that when a content percentage of a fundamental wave is 100%, a total content percentage calculated by the formula (A2+B2+C2+D2+E2+F2)05 is at most 11% where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component, C is a content percentage of an eleventh order component, D is a content percentage of a thirteenth order component, E is a content percentage of a seventeenth order component, and F is a content percentage of a nineteenth order component.
In a third aspect of the invention, the very high speed permanent magnet type electric rotating machine system in the first or second aspect of the invention is such that the electromagnetic steel sheet ring is made of a high tensile strength electromagnetic steel sheet, of which tensile strength is at least 70 kg/mm2.
In a fourth aspect of the invention, there is provided a very high speed permanent magnet type electric rotating machine system comprising a permanent magnet type synchronous motor including a stator having armature windings wound in a plurality of slots formed in a stator core, and a rotor including an electromagnetic steel sheet ring provided on an outer periphery of a shaft made of a conductive magnetic material, and conductive permanent magnets inserted into permanent magnet insertion holes in the electromagnetic steel sheet ring, and an inverter for driving the permanent magnet type synchronous motor, the improvement comprising an reactor interposed between the inverter and the permanent magnet type synchronous motor, and wherein content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor from the inverter are such that when a content percentage of a fundamental wave is 100%, a total content percentage calculated by the formula (A2+B2+C2+D2+E2+F2)05 is at most 14% where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component, C is a content percentage of an eleventh order component, D is a content percentage of a thirteenth order component, E is a content percentage of a seventeenth order component, and F is a content percentage of a nineteenth order component.
In a fifth aspect of the invention, the very high speed permanent magnet type electric rotating machine system of the fifth aspect of the invention is such that the electromagnetic steel sheet ring is made of a high tensile strength electromagnetic steel sheet, of which tensile strength is at least 80 kg/mm2.
In a sixth aspect of the invention, the very high speed permanent magnet type electric rotating machine system of one of the first to fifth aspects of the invention is used for an air generating source.
That is, magnetic flux of the permanent magnet is conducted to the stator through the shaft of the rotor and a CFRP. Further, when the permanent magnet type motor is driven by an inverter operating at a fundamental frequency of at least several hundreds of HZ, harmonic magnetic flux is induced due to harmonic current supplied from the inverter. Influential orders of the harmonic current are 5, 7, 11, 13, 17 and 19 times as high as that of the fundamental frequency, which will generate harmonic losses on the constituent members. As a result of various experiments, it was found that a highest harmonic loss was generated on the shaft to amount to as high as several kW, which does not make any very high speed permanent magnet type synchronous motor practical.
However, with the very high speed permanent magnet type electric rotating machine system according to the first aspect of the invention, the electromagnetic steel sheet ring made of a magnetic material is provided on the outer periphery of the shaft of the rotor, the reactor is inserted between the inverter and the permanent magnet type synchronous motor, and content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor are adjusted such that when a content percentage of a fundamental wave is 100%, a content percentage B of a seventh order component is at most 10% and a total content percentage is made equal to or less than a certain value so as to satisfy the relationship (A less than C less than B) where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component thereof, and C is a content percentage of a ninth order component thereof, thereby enabling realizing a very high speed permanent magnet type electric rotating machine system, in which harmonic loss of neodymium magnets as well as harmonic loss of the shaft is greatly reduced and loss of the rotor can be reduced to several hundreds of W.
Further, with the very high speed permanent magnet type electric rotating machine system according to the second aspect of the invention, the electromagnetic steel sheet ring made of a magnetic material is provided on the outer periphery of the shaft of the rotor, the reactor is inserted between the inverter and the permanent magnet, and content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor from the inverter are adjusted such that when a content percentage of a fundamental wave is 100%, a total content percentage calculated by the formula (A2+B2+C2+D2+E2+F2)05 becomes at most 11% where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component, C is a content percentage of an eleventh order component, D is a content percentage of a thirteenth order component, E is a content percentage of a seventeenth order component, and F is a content percentage of a nineteenth order component, thereby enabling realizing a very high speed permanent magnet type electric rotating machine system, in which harmonic loss of neodymium magnets as well as harmonic loss of the shaft is greatly reduced and loss of the rotor can be reduced to several hundreds of W. Further, the above-mentioned adjustment is effected such that the reactor is adjusted to a value in the range of from 0.2 to 0.1 xcexa9 so as to make the total content percentage equal to or less than 11%.
With the very high speed permanent magnet type electric rotating machine system according to the third aspect of the invention, the rotor according to the first or second aspect of the invention is employed and a high tensile strength electromagnetic steel sheet is used to form the electromagnetic steel sheet ring of magnetic materials and provided on the outer periphery of the shaft, whereby the rotor can be rotated at very high speeds.
With the very high speed permanent magnet type electric rotating machine system according to the fourth aspect of the invention, the electromagnetic steel sheet ring is provided on the outer periphery of the shaft, the permanent magnets are inserted in the permanent magnet insertion holes in the electromagnetic steel sheet ring, the reactor is inserted between the inverter and the permanent magnet type synchronous motor, and content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor from the inverter are adjusted such that when a content percentage of a fundamental wave is 100%, a total content percentage calculated by the formula (A2+B2+C2+D2+E2+F2)05 becomes at most 14% where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component, C is a content percentage of an eleventh order component, D is a content percentage of a thirteenth order component, E is a content percentage of a seventeenth order component, and F is a content percentage of a nineteenth order component, thereby enabling realizing a very high speed permanent magnet type electric rotating machine system, in which harmonic loss of neodymium magnets as well as harmonic loss of the shaft is greatly reduced and loss of the rotor can be reduced to several hundreds of W.
Further, with the very high speed permanent magnet type electric rotating machine system according to the fifth aspect of the invention, the electromagnetic steel sheet ring is made of a high tensile strength electromagnetic steel sheet, of which tensile strength is at least 80 kg/mm2.
With the air generating source using the very high speed permanent magnet type electric rotating machine system, according to the sixth aspect of the invention, the very high speed permanent magnet type electric rotating machine system is enhanced in efficiency, so that an air generating source can be provided, which generates a high output with the same input.